You aren't obligated to keep people in your life, especially if they leave you feeling down all the time. Sometimes, you have to do what's best for you.
Live the best life you possibly can and forget the resentment holding you back.
Engage in activities that fill your heart with happiness, and make your soul sing in joy.
Make sure you take care of yourself, even if it's in seemingly small ways. Every bit contributes to you keeping both your mind and body healthy.